Interfacing LED's

    The first thing usually done while learning any microcontroller or embedded system is blinking an LED. The circuit below shows the circuit for Interfacing an LED.

 Here an LED is connected to the first pin of port0 (P0.0). The assembly program given below is simple and self explanatory.

;************************************************* ; ;Program: Blinking LED. ;Author: Mahesh ;Description: Blinks an LED connected to P0.0 ;continuously ; ;************************************************* led equ P0.0 org 00h up:  setb led        ;Turn ON the LED      acall delay     ;call delay subroutine      clr led         ;Turn OFF the LED      acall delay     ;call delay subroutine      sjmp up         ;Loop  delay:mov r7,#0ffh   ;delay subroutine loop:mov r6,#0ffh      djnz r6,$          djnz r7,loop      ret end